Light-induced swirling and locomotion

Abstract: Photomechanical liquid crystal elastomers (LCEs) are responsive polymers that can convert light directly into mechanical deformation. This unique feature makes these materials an attractive candidate for soft actuators capable of remote and multi-mode actuation. In this work, we propose a three-dimensional multi-scale model of the nonlinear and nonlocal dynamics of fibers of photomechanical LCEs under illumination. We use the model to show that a pre-stressed helix-like fibers immersed in a fluid can undergo a periodic whirling motion under steady illumination. We analyze the photo-driven spatiotemporal pattern and stability of the whirling deformation, and provide a parametric study. Unlike previous work on photo-driven periodic motion, this whirling motion does not exploit instabilities in the form of snap-through phenomena, or gravity as in rolling. We then show that such motion can be exploited in developing remote controlled bio-inspired microswimmers and novel micromixers.